This invention relates generally to an iris information acquisition apparatus, an iris identification apparatus and the others, and particularly to techniques capable of remarkably reducing time from an image pickup of an iris image to generation of an iris code, and capable of simplifying the iris information acquisition apparatus, the iris identification apparatus and the like.
Security systems accompanying development of high computerization in recent years require high reliability and convenience. In these security systems, for example, key, password, ID card, IC card, signature, voiceprints, fingerprints, biometric features (face pattern, set of teeth, retina, iris pattern and so on) are used as recognition means. Generally, in order of description of the above recognition means, degree of problems that these recognition means must be carried, are forgotten, are difficult to operate, are lost, are forged, etc. decreases, with the result that the recognition means have high reliability while the security systems become complicated and expensive.
The fingerprints among the above recognition means have been adopted by the police etc. of the whole world in the past and have been the most familiar personal identification means. However, a pattern of the fingerprints at the time of registration is not identical with that of the fingerprints at the time of matching since the fingertips are soft, and also, a false acceptance rate which is a probability of deciding the patterns identical in spite of the different patterns of the fingerprints and a false rejection rate which is a probability of deciding the patterns different in spite of the identical patterns of the fingerprints are said to become about 10 to 20% since the fingerprints themselves are easy to transform.
Also, in a system for matching a blood vessel pattern on the retina, to detect this blood vessel pattern, behavior of looking through a device for detecting the blood vessel pattern is forced and the false rejection rate becomes high due to influence of retinitis (hemorrhage of fundus oculi, white patch, exudation) and so on.
On the contrary, the iris pattern which has a demerit of hiding the iris in an eyelid is said to be almost immutable until death since two years of age, and a personal identification rate using the iris pattern has high reliability and thus, the iris pattern is said to be the most excellent personal identification system. As shown in FIG. 15, the iris means a region 101 having a pattern drawn radially on the outside of a pupil 100.
The personal identification system using such the iris pattern is disclosed in U.S. Pat. No. 5,291,560, for example. Also, an xe2x80x9cIrisIdentxe2x80x9d (registered trademark) system made of SENSAR Inc. in the U.S.A. is used as a practical system. As shown in FIG. 16, this system roughly comprises two illumination parts 110, a camera part 111, a processing part 112, and cables 113 for connecting the camera part 111 to the processing part 112. And then, the processing part 112 is connected to a host computer (not shown). A personal recognition processing using the system is generally performed according to the following procedure.
First, a three-dimensional position of the eye of human locating at the front of the camera part 111 is calculated on the basis of stereoscopic vision by two wide-angle cameras in the camera part 111. This calculation is performed by the processing part 112 on the basis of image pickup information fed from the wide-angle cameras.
Secondly, a zoom camera in the camera part 111 is focused on the three-dimensional position fed from the processing part 112 and zoom magnification is inversely proportioned to the distance.
Thirdly, by this, an iris image caught by the zoom camera is taken with a CCD image sensor of said zoom camera and is fed to the processing part 112.
Fourthly, the processing part 112 divides an iris portion (a region from the inner boundary to the outer boundary of the iris) in the taken iris image into eight concentric bands so as not to be influenced by variations in the pupil diameter. This is because the inside of the iris portion stretches and contracts in response to change in the pupil and thus the iris pattern itself stretches and shrinks. But, the outside of the iris portion does not change.
Fifthly, a convolution operation using a two-dimensional Gabor filter for feature extraction is performed every the divided band and a band-pass filtering is performed and the result is formed in binary code.
Sixthly, an iris code of 256 bits is calculated from the obtained binary information every the band.
Lastly, The processing part 112 performs personal identification by deciding whether the calculated iris code is matched with the previously registered iris code or not. This personal identification may be performed through the host computer (not shown) connected to the processing part 112.
In the personal identification system using the iris pattern mentioned above, however, the normal CCD image sensor arranged in a grid shape is used when the iris image is acquired, so that a coordinate of the iris portion of the iris image taken by the CCD image sensor must be transformed from an orthogonal coordinate system to a polar coordinate system and further, the convolution operation to each the transformed band must be performed. Since it takes an enormous time to process the coordinate transformation or the convolution operation, the is personal identification system had a problem that such the coordinate transformation or the convolution operation greatly affects a delay in processing time of the whole identification processing.
Although the above problem may be solved by enhancing the calculation capability of the processing part 112, a new problem has arisen in that the enhancement of the calculation capability requires a high cost naturally, and obstructs miniaturization and weight-saving of the personal identification system including the processing part 112.
Accordingly, it is an object of the present invention to provide an iris recognition and identification method and its system capable of removing the above-mentioned problems of the prior art.
It is another object of the present invention to provide an iris recognition and identification method and its system capable of remarkably reducing time required from image: pickup of an iris image to generation of an iris code as well as of simplifying the system.
It is yet another object of the present invention to provide an iris recognition and identification method and its system capable of remarkably reducing time required from image pickup of an iris image to generation of an iris code and further capable of simplifying the system.
According to an aspect of the present invention, there is provided an iris information sensor comprising an image pickup sensor having a group of photoelectric conversion pixels arranged in polar coordinates, wherein image light from an iris region of an eye is focused on the image pickup sensor so that the center of an iris image formed on the sensor substantially matches with the pole of the polar coordinates of the sensor and the photoelectric conversion pixels of the sensor are sequentially scanned to read out an iris image signal.
The image pickup sensor may be made of a group of pixels arranged in concentric circles.
The image pickup sensor may also be made of a group of pixels arranged in a spiral shape extending in the radial direction.
According to another aspect of the present invention, there is provided an iris information acquisition apparatus for obtaining image information of an iris region, comprising:
an image pickup sensor having a group of photoelectric conversion pixels arranged in polar coordinates;
image pickup optical system means for focusing image light from the iris region on the image pickup sensor;
optical axis operation control means for matching the center of an iris image formed on the sensor with the pole of the polar coordinates of the sensor;
region determination means for determining the iris region by acquiring the inner and outer diameters of the iris according to an iris image signal obtained by the sensor; and
read scan means for scanning the determined iris region in a predetermined sequence and obtaining an output value corresponding to information of the iris region.
The read scan means for scanning the determined iris region may scan the determined iris region at least in the tangential direction.
The read scan means for scanning the determined iris region may scan the determined iris region in the tangential and radial directions every given width.
The read scan means may divide the determined iris region into predetermined concentric ring bands and determine the number of pixels of the radial direction of each ring band, and also read the output value corresponding to information of each ring band in which weighted mean is performed according to the number of pixels.
The region determination means may determine the iris region according to amplitude of a feature extraction signal, said feature extraction signal obtained by passing the image signal through a band-pass filter, said image signal obtained by scanning the image pickup sensor in the tangential direction.
The said region determination means may determine the iris region according to level variation in the image signal obtained by the scan in the radial direction of the image pickup sensor.
The optical axis operation control means may calculate the direction and size of an error between the center of the iris image formed on the image pickup sensor and the pole of the polar coordinates of the sensor to control a matching of the center of the iris image with the pole of the polar coordinates of the sensor, by further passing the feature extraction signal through a low-pass filter, said feature extraction signal obtained by passing the image signal through the band-pass filter, said image signal obtained by scanning the image pickup sensor in the tangential direction.
The iris information acquisition apparatus may further comprises illumination means for irradiating illumination light to the eye and a group of light receiving elements for receiving reflected light from the eye of the illumination light, the optical axis operation control means controlling a matching of the center of the iris image with the pole of the polar coordinates of the image pickup sensor according to an amount of receiving light of the group of light receiving elements.
According to still another aspect of the present invention, there is provided an iris information acquisition apparatus for obtaining image information of an iris region of an eye, comprising:
an image pickup sensor having a group of photoelectric conversion pixels arranged in polar coordinates;
image pickup optical system means for focusing image light from the iris region on the image pickup sensor;
illumination means for irradiating illumination light to the eye having the iris;
optical axis operation control means for matching the center of an iris image formed on the sensor with the pole of the polar coordinates of the sensor;
light adjustment control means for definitely controlling the inner diameter of the iris image formed on the sensor by irradiating visible light to the eye having the iris from the illumination means and adjusting an amount of the light and defining the pupil diameter; and
read scan means for scanning the sensor in a predetermined sequence and reading image information of the iris region.
The image pickup optical system means may include a zoom lens and definitely keeps the outer diameter of the iris image formed on the image pickup sensor by the zoom lens.
The pixel of the image pickup sensor each may have a light receiving region with an approximately rhombic shape having each diagonal in the radial and tangential directions of the polar coordinates.
The pixel of the image pickup sensor each may also be arranged in a region with an approximately rhombic shape surrounded by the light receiving regions with the approximately rhombic shape.
The iris information acquisition apparatus may further comprise iris code generation means for generating an iris code according to the output value read by the read scan means.
The iris code generation means may comprise comparison means for comparing a band-pass filter receiving the output value and output of the band-pass filter with a predetermined threshold value.
The iris code generation means may generate the iris code by comparing the output value of a plurality of continuous pixels with output of a target pixel.
It is possible to add information on the effective range of the iris region to the iris code.
It is also possible to add information on resolution of the image pickup sensor to the iris code.
It is further possible to add information on tilt of the eye to the iris code.
It is further possible to add information on whether the iris code is the right eye or the left eye to the iris code.
The iris information acquisition apparatus may further comprises a group of light receiving elements for receiving reflected light from the eye of light irradiated by said illumination means, said optical axis operation control means controlling a matching of the center of the iris image with the pole of the polar coordinates of the image pickup sensor according to an amount of receiving light of the group of light receiving elements.
The optical axis operation control means may calculate the direction and size of an error between the center of the iris image formed on the image pickup sensor and the pole of the polar coordinates of the sensor to control a matching of the center of the iris image with the pole of the polar coordinates of the sensor, by further passing the feature extraction signal through a low-pass filter, said feature extraction signal obtained by passing the image signal through the band-pass filter, said image signal obtained by scanning the image pickup sensor in the tangential direction.
The optical axis operation control means may control a matching of the center of the iris image formed on the image pickup sensor by moving a mirror placed in an optical path between the eye of the iris of a subject and the sensor with the pole of the polar coordinates of the sensor.
The optical axis operation control means may control a matching of the center of the iris image formed on the image pickup sensor by moving the sensor with the pole of the polar coordinates of the sensor.
The optical axis operation control means may control a matching of the center of the iris image formed on the image pickup sensor by a vertical angle variable prism placed in an optical path between the eye of the iris of a subject and the sensor with the pole of the polar coordinates of the sensor.
The optical axis operation control means may control a matching of the center of the iris image formed on the image pickup sensor by mutually translating a plurality of lenses placed in an optical path between the eye of the iris of a subject and the sensor with the pole of the polar coordinates of the sensor.
The image pickup sensor may comprise a linear sensor in which pixels are arranged in the radial direction and rotation driving means for synchronously rotating the linear sensor around the pole of the polar coordinates, and a function equivalent to the group of the pixels of the polar coordinates may be achieved by the rotation of the linear sensor through the rotation driving means.
The pixel constructing the image pickup sensor each may be made of a MOS sensor or a CCD sensor.
The pixel constructing the image pickup sensor each may be made of a device for detecting edge information electrically or optically.
The pixel density in the radial direction of each pixel of the image pickup sensor may correspond to the rate of stretching and shrinking of the iris.
The image pickup sensor may be made of a group of pixels arranged in a spiral shape extending in the radial direction.
According to still another aspect of the present invention, there is provided an iris identification apparatus for acquiring an iris code representing information of an iris region of an eye and comparing and matching the acquired iris code with a previously registered iris code, comprising:
an image pickup sensor having a group of photoelectric conversion pixels arranged in polar coordinates;
image pickup optical system means for focusing image light from the iris region on the image pickup sensor; optical axis operation control means for matching the center of an iris image formed on the sensor with the pole of the polar coordinates of the sensor;
region determination means for determining the iris region by acquiring the inner and outer diameters of the iris according to an iris image signal obtained by the sensor;
read scan means for dividing the determined iris region into predetermined concentric ring bands and determining the number of pixels of the radial direction of each ring band and reading the output value corresponding to information of each ring band in which weighted mean is performed according to the number of pixels;
iris code generation means for generating the iris code according to the output value; and
comparison means for matching the generated iris code with the previously registered iris code.
The matching means may match the iris region including a region hidden by the eyelids.
The iris identification apparatus may further comprise a nonvolatile memory for storing the previously registered iris code, and means for encoding or ciphering the matched result in order to secure security.
The iris identification apparatus may further comprise means for adjusting identification determination level used when matching the generated iris code with the previously registered iris code.
According to still another aspect of the present invention, there is provided an iris identification apparatus for acquiring information of an iris region of an eye and comparing and matching the acquired information of the iris region with information of an iris region registered previously, comprising:
an image pickup sensor having a group of photoelectric conversion pixels arranged in polar coordinates;
image pickup optical system means for focusing image light from the iris region on the image pickup sensor;
illumination means for irradiating illumination light to the eye having the iris;
optical axis operation control means for matching the center of an iris image formed on the sensor with the pole of the polar coordinates of the sensor;
light adjustment control means for definitely controlling the inner diameter of the iris image formed on the sensor by irradiating visible light to the eye having the iris from the illumination means and adjusting an amount of the light and defining the pupil diameter;
read scan means for scanning the sensor in the tangential and radial directions and reading the information of the iris region; and
matching means for matching the information of the iris region read by the read scan means with the information of the iris region registered previously through pattern matching.
The image pickup optical system means may include a zoom lens and definitely keeps the outer diameter of the iris image formed on the image pickup sensor by the zoom lens.
The matching means may match the iris region including a region hidden by the eyelids.
The iris identification apparatus may further comprise a nonvolatile memory for storing the previously registered iris code, and means for encoding or ciphering the matched result in order to secure security.
The iris identification apparatus may further comprise means for adjusting identification determination level used when said matching means performs said matching.
According to still another aspect of the present invention, there is provided an iris identification method for acquiring an iris code representing information of an iris region of an eye and comparing and matching the acquired iris code with a previously registered iris code, comprising the steps of:
using an image pickup sensor having a group of photoelectric conversion pixels arranged in polar coordinates;
focusing image light from the iris region on the image pickup sensor through image pickup optical system means;
matching the center of an iris image formed on the sensor with the pole of the polar coordinates of the sensor through optical axis operation control means;
determining the iris region by acquiring the inner and outer diameters of the iris according to an iris image signal obtained by the sensor;
dividing the determined iris region into predetermined concentric ring bands and determining the number of pixels of the radial direction of each ring band and reading the output value corresponding to information of each ring band in which weighted mean is performed according to the number of pixels;
generating the iris code from the output value through iris code generation means; and
performing personal identification by matching the generated iris code with the previously registered iris code.
It is possible to match the iris region including a region hidden by the eyelids.
The previously registered iris code may be stored in a nonvolatile memory, and the iris identification method may further comprise the steps of encoding or ciphering the matched result in order to secure security.
It is possible to make identification determination level when performing personal identification adjustable from external or internally.
According to still another aspect of the present invention, there is provided an iris identification method for acquiring information of an iris region of an eye and comparing and matching the acquired information of the iris region with information of an iris region registered previously, comprising the steps of:
using an image pickup sensor having a group of photoelectric conversion pixels arranged in polar coordinates;
focusing image light from the iris region on the image pickup sensor through image pickup optical system means;
irradiating illumination light to the eye having the iris through illumination means;
matching the center of an iris image formed on the sensor with the pole of the polar coordinates of the sensor through optical axis operation control means;
definitely controlling the inner diameter of the iris image formed on the sensor by irradiating visible light to the eye having the iris from the illumination means and adjusting an amount of the light and defining the pupil diameter;
scanning the sensor in the tangential and radial directions and reading the information of the iris region through read scan means; and
performing personal identification by matching the information of the iris region read by the read scan means with the information of the iris region registered previously through pattern matching.
The image pickup optical system means may include a zoom lens and may definitely keep the outer diameter of the iris image formed on the image pickup sensor by the zoom lens.
It is possible to match the iris region including a region or regions hidden by the eyelids.
It is possible to store the previously registered iris code in a nonvolatile memory, and may further comprise the steps of encoding or ciphering the matched result in order to secure security.
It is possible to make identification determination level when performing personal identification adjustable from external or internally.